White matter tract integrity (WMTI) can characterize brain microstructure inareas with highly aligned fiber bundles. Several WMTI biomarkers have now beenvalidated against microscopy and provided promising results in studies of braindevelopment and aging, and in a number of brain disorders. Currently, WMTI ismostly used in dedicated animal studies and clinical studies of slowlyprogressing diseases but has not yet emerged as a routine clinical tool. Tothis end, a less data intensive experimental method would be beneficial byenabling high resolution validation studies, and ease clinical applications byspeeding up data acquisition compared to typical diffusion kurtosis imaging(DKI) protocols utilized as part of WMTI imaging. Here, we evaluate WMTI basedon recently introduced axially symmetric DKI which has lower data demand thanconventional DKI. We compare WMTI parameters derived from conventional DKI tothose calculated analytically from axially symmetric DKI. We employ numericalsimulations, as well as data from fixed rat spinal cord (1) and in vivo human(3) and rat brain (4). Our analysis shows that analytical WMTI based on axiallysymmetric DKI with sparse data sets (19 images) produces WMTI metrics thatcorrelate strongly with estimates based on traditional DKI data sets (60 imagesor more). We demonstrate the preclinical potential of the proposed WMTItechnique in in vivo rat brain (300 {\mu}m isotropic resolution with wholebrain coverage). WMTI parameter estimates are subject to a duality leading totwo solution branches dependent on a sign choice which is currently debated.Results from both of these branches are presented and discussed throughout ouranalysis. The proposed fast WMTI approach may be useful for preclinicalresearch and e.g. clinical evaluation of patients with traumatic white matterinjuries or symptoms of neurovascular or neuroinflammatory disorders.
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